CONSOLIDATED STATEMENTS OF CASH FLOWS $ in Millions	12 Months Ended
	Dec. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)
Cash Flows from Operating Activities:
Net income	$ 174.7	$ 157.7	$ 157.7
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	91.2	95.0	58.6
Provision for accounts receivable allowances	3.7	3.3	12.1
Provision (benefit) for deferred income taxes	18.9	11.2	(5.1)
Share-based compensation	39.3	31.5	24.0
Write-off of loan costs	18.9	0.0	0.0
Workers' Compensation provision	3.3	3.6	2.9
Other	(9.0)	(11.7)	(6.6)
Changes in operating assets and liabilities, net of effects of acquisitions:
Accounts receivable	(24.3)	(90.7)	(50.5)
Prepaid expenses and income taxes	20.8	(14.8)	11.9
Income taxes payable	(2.2)	2.1	0.6
Accounts payable	(7.3)	23.3	0.3
Accrued payroll and contract professional pay	5.0	25.4	1.0
Workers' compensation loss reserve	(3.2)	(3.3)	(2.6)
Increase Decrease In Operating Right of Use Asset	28.0	0.0	0.0
Increase (Decrease) In Operating Lease Liability	26.7	0.0	0.0
Other	5.7	1.8	2.7
Net cash provided by operating activities	313.2	287.4	196.4
Cash Flows from Investing Activities:
Cash paid for property and equipment	(32.7)	(28.7)	(24.3)
Cash paid for acquisitions, net of cash acquired	(116.4)	(760.2)	(25.9)
Other	0.0	0.2	0.1
Net cash used in investing activities	(149.1)	(788.7)	(50.1)
Cash Flows from Financing Activities:
Principal payments of long-term debt	(736.2)	(286.0)	(105.0)
Proceeds from long-term debt	653.0	822.0	37.0
Proceeds from option exercises and employee stock purchase plan	12.7	9.4	7.8
Payment of employment taxes related to release of restricted stock awards	(12.2)	(5.6)	(14.9)
Repurchase of common stock	(20.0)	0.0	(60.1)
Debt issuance or amendment costs	(7.8)	(22.5)	(3.3)
Other	0.0	(9.5)	0.0
Net cash provided by (used in) financing activities	(110.5)	507.8	(138.5)
Effect of exchange rate changes on cash and cash equivalents	(0.2)	(1.4)	1.8
Net Increase in Cash and Cash Equivalents	53.4	5.1	9.6
Cash and Cash Equivalents	95.2	41.8	36.7
Supplemental Disclosure of Cash Flow Information
Income taxes	56.6	21.4	55.3
Interest	44.9	51.0	24.1
Non-Cash Investing and Financing Activities:
Unpaid portion of additions to property and equipment	2.2	2.5	2.3
Unpaid portion of debt issuance or amendment costs	$ 1.3	$ 0.0	$ 0.0